1. Field of the Invention
This invention generally relates to a rotary broom machine especially adapted for construction and maintenance work on a railway roadbed or track, as for dressing the surface of the ballast bed between and along the sides of the rails and for leveling and distributing ballast over the bed.
Particularly, the invention is concerned with a sweeper bristle element used in conjunction with a rotating drum. A plurality of the bristles are mounted on support means attached to the drum and the drum is rotated by the associated machinery to thereby clean the track and level the roadbed.
2. Description of the Prior Art
This invention constitutes an improvement over prior U.S. Pat. No. 4,184,223 titled "Sweeper Bristle Element", the patentee therein being the applicant herein; the disclosure of U.S. Pat. No. 4,184,223 is incorporated by reference herein.
Prior to the advent of the subject matter of U.S. Pat. No. 4,184,223, new ballast dumped upon a track roadbed was roughly distributed by a blade-like plow or moldboard. Since this procedure failed to produce the desired relationship between the rail ties and the ballast level, several broom type implements were developed so as to provide the desired ballast-tie relationship, to wit, the ballast being level with or slightly below the tops of the ties. The sweeping action of the broom bristles against the highly abrasive ballast subjected the bristles to heavy wear and consequently, short bristle and broom life resulted.
One example of these prior art constructions included bristles comprised of lengths of steel cable removably fastened to a mandrel or drum of the broom and encased in heavy duty hose sections to control fraying of the cable. This design was found to yield extremely short life span, sometimes as little as two hours, before replacement was required, and such replacement was quite time consuming and costly in terms of man-hours.
To overcome these problems, the bristle element of U.S. Pat. No. 3,649,984 to Kershaw was developed but unfortunately this bristle, made of a core of parallel straight spring-steel splines or wires fixed together at one end in a detachable coupling and encased in a resilient sheath which binds the splines in mutually supporting relation and distributes flexing stress away from the fixed end, is quite complex to manufacture and expensive to assemble. Further, the life span of the bristles of Kershaw, et al. is not significantly longer than that of bristles prior thereto.
A further advance in the art comprised the subject matter of U.S. Pat. No. 4,184,223. Therein, the patentee (applicant herein) found that a solid bristle of elastomeric material would overcome many of the above discussed disadvantages. Therein, each bristle element comprises a solid hard rubber elastomeric stem, preferably 80 durometer as measured on a Shore, type A, durometer gauge and a solid softer rubber toe integrally laminated thereon, the toe being preferably 60 durometer, again, as measured on a Shore, type A, durometer gauge. The toe is laminated at one end of the stem on one side thereof with the other stem end being adapted to be connected to a rotary broom drum. The elastomeric nature of the bristles renders them much more resistant to wear from abrasive contact with ballast. The bristles are attached to the drum with a combination of nuts, bolts and a clamping member on the side of the bristles opposite the side bearing against the drum. As the drum is rotated, centrifugal force is imparted on the stem and toe, causing loose material contacting the toe to be driven away therefrom.